Electrochemical biosensor based on botryosphaeran as a novel biomaterial for laccase immobilization

A new architecture for a novel biosensing platform is proposed using the exopolysaccharide, botryosphaeran (EPSB) and a crude laccase extract (CLE)[1] from the ascomyceteous fungus Botryosphaeria rhodina MAMB- 05. Laccase was immobilized by physical adsorption on botryosphaeran using a carbon black paste electrode (CBPE) modified with gold nanoparticles (AuNps). The physicochemical characterization of the biosensor was performed by using transmission electron microscopy and electrochemical impedance spectroscopy. The performance of this novel biosensing platform was evaluated by choosing hydroquinone (HQ) as a typical model of a phenolic compound. Different sensors were prepared to evaluate the contribution of each modifier employed (Fig. 1). All electrodes showed better responses than the unmodified CBPE, and the highest analytical signal was obtained using the immobilized laccase on the CBPE-AuNps support. This could be attributable to the electrocatalytic properties of AuNps[2] associated with the stable immobilization mechanism proposed, by EPSB, that promotes a biocompatible microenvironment, since both biomaterials were produced by the same fungus, and the EPSB did not affect laccase activity. Experimental variables such as laccase concentration, the pH value and operational parameters of the electroanalytical technique were optimized. Using square-wave voltammetry, we observed a linear dependence of cathodic peak current and hydroquinone concentration in the range of 2.00 - 56.5 μmol L−1 with a detection limit of 0.143 μmol L−1 (Fig. 2). The proposed methodology was successfully applied in determining HQ in a dermatological cream, and in environmental and synthetic biological samples. Good selectivity was presented in the presence of other organic compounds, inorganic ions, and attests the potential application of this novel biosensing platform in complex matrices. The different aspects regarding the operational stability of this laccase-biosensor were evaluated, and showed good intra-day and inter-day repeatability, as well as long-storage stability.